Telomeres: A New Twist on Aging

Why are some people in their 70s as vigorous and healthy as the average 55-year-old, while some people in their 50s are more like 75-year-olds? Clearly, humans age at different rates. Researchers have proposed many ways to determine a person’s “biological age,” as opposed to chronological age, using criteria such as blood pressure, heart rate, exercise capacity, and even handgrip.

One of the most promising ways to evaluate biological age is to analyze genetic material—notably telomeres, “caps” on the ends of DNA strands that make up chromosomes (picture the plastic tips on shoelaces). Telomeres help protect DNA from damage as cells repeatedly divide and DNA replicates. Over time, telomeres progressively shorten, which is a sign of cellular aging. When telomeres get too short and cannot be repaired, chromosomes fray and the cells can no longer divide.

Having a high percentage of short telomeres is associated with some cancers, cardiovascular disease, and other age-related disorders. (On the other hand, extralong telomeres are associated with increased risk of a few cancers.) It’s estimated that at least half of the variability in telomere length is inherited; the rest is influenced by lifestyle and environmental factors, such as diet, physical activity (or lack thereof), obesity, smoking, and exposure to toxins and pollutants. The 2009 Nobel Prize in Physiology or Medicine went to three scientists for their work on telomeres. Several people have asked me if I think that telomere testing is worthwhile.

Here’s a sampling of the research:

Studies have found that people (or lab animals) who exercise regularly tend to have less telomere shortening than their sedentary counterparts. This may be one way that exercise helps keep us healthy. It’s unclear how long or how intensely you have to exercise to achieve this (some studies point to moderate activity, others strenuous). A study from Brigham Young University, published in Preventive Medicine in 2017, found that it took vigorous exercise—jogging at least 30 or 40 minutes most days of the week—to lengthen telomeres substantially, enough to represent an estimated nine-year decease in biological aging compared to being sedentary.

In a 2012 study in Mutagenesis, Italian researchers found that people who ate lots of vegetables tended to have longer telomeres. Other studies have linked various vitamins and minerals with longer telomeres.

A study in Mayo Clinic Proceedings in 2015 found that people who spent the most time at TV or computer screens tended to have the shortest telomeres, even after factors such as age and exercise were controlled for.

A study by one of the Nobel Prize winners, published in Mutation Research, found associations between psychological stress, childhood adversity, long-term depression, and telomere shortening.

A small study in Lancet Oncology found that men with prostate cancer who followed Dr. Dean Ornish’s diet (low-fat, plant-based) and lifestyle plan (exercise, stress management, social support) for five years had increases in telomere length.

Despite such preliminary research, it’s still not certain what the exact connection is between telomere length, disease, and aging. Are short telomeres a cause of aging and diseases, a consequence of them, or simply a biomarker for an unhealthy lifestyle and thus elevated risk? If scientists can find ways to maintain or increase telomere length, would that help keep people healthy? No one knows yet. But that hasn’t stopped companies from promoting telomere testing (using blood or saliva) to doctors and the general public as a way to predict future health. Nor has it stopped marketers from promoting dietary supplements (containing astragalus, resveratrol, and many other compounds) that they claim—with little or no clinical evidence—will improve health by lengthening telomeres or protecting them from damage.

My bottom line: This is an exciting field of research, but at this point there are far more unknowns than knowns. So far, the findings reinforce commonsense advice about a healthy lifestyle—not smoking, exercising regularly, controlling stress, having a healthy diet, and so on.

As for commercial telomere testing, its accuracy and practical value are unproven, and the interpretation of the findings is fraught with problems. Such commercial testing is not ready for prime time. As an expert in telomere dysfunction wrote in Mayo Clinic Proceedings in July 2018, such testing, for now, “may be considered a form of molecular palm reading.”